Dry cleaner

ABSTRACT

According to the present invention, a highly safe dry cleaner is provided, which ensures safety without the danger of ignition in a drying process even if so-called microcomputer runaway occurs. The dry cleaner includes a relay sequence controlling circuit ( 71 ). The relay sequence controlling circuit ( 71 ) includes a serial connection of a first valve (V 27 ) to be controlled, a first switch ( 77 ) which controls the turn-on of the first valve (V 27 ) and a second contact ( 76   a ) provided in a second relay ( 76 ). A detection circuit ( 79 ) which controls the second contact ( 76   a ) is connected to the serial connection. Thus, the first valve (V 27 ) is maintained in an inactive state irrespective of a first switch turn-on control performed by a control section ( 81 ) until the detection circuit ( 79 ) performs a predetermined operation to turn on the second contact  76   a.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a dry cleaner and, more specifically,to a dry cleaner which performs a washing process employing a flammablesolvent, a liquid removing process and a drying process.

2. Description of Related Art

Dry cleaners are conventionally known, which are adapted to wash laundrywith a flammable solvent such as a petroleum-based solvent, remove thesolvent from the washed laundry, and dry the laundry by applying hot airheated by a heater to the laundry for vaporization of the solvent.

Meanwhile, the petroleum-based solvent is highly flammable. Therefore,if solvent gas resulting from the vaporization of the solvent from thelaundry is present at a higher concentration during the drying of thelaundry, the solvent gas is liable to be ignited by the heat of theheater, resulting in momentary flash or explosion.

A known dry cleaner designed to prevent such accidents includes: a drumin which laundry is contained, and a washing process, a liquid removingprocess and a drying process are performed; an air circulation ductthrough which air is circulated to the drum; a drying heater of a steamheating type for heating the air flowing through the air circulationduct; a steam valve which is opened and closed for supplying steam tothe drying heater; a drum inlet temperature sensor provided in the aircirculation duct for measuring the temperature of gas to be supplied tothe drum; a drum outlet temperature sensor which measures thetemperature of gas having passed through the drum; and a control sectionincluding a microcomputer and the like for controlling the steam valveand the temperature sensors (see, for example, Japanese UnexaminedPatent Publication No. 2005-218881).

In the drying process, a drum outlet temperature is changed according tothe amount of solvent contained in the laundry. That is, if the laundrycontains a greater amount of solvent, the amount of solvent vaporizedfrom the laundry is relatively great, so that the drum outlettemperature is relatively low. If a drum inlet temperature is elevated,for example, by promoting the heating with the steam valve being openedwhen the drum outlet temperature is lower, the solvent vaporizationamount is further increased. If an atmosphere containing the solvent gasat a concentration higher than a safety value (e.g., 6.0 vol % where thesolvent is gasoline No. 5) occurs in the drum, there is the danger ofignition.

In the dry cleaner disclosed in Japanese Unexamined Patent PublicationNo. 2005-218881, the microcomputer monitors the drum outlet temperatureand controls the opening and closing of the steam valve to control thetemperature of the circulation air supplied from a drum inlet, therebypreventing an excessive increase in the amount of the solvent vaporizedfrom the laundry and hence preventing the solvent gas concentration fromexceeding the safety value for elimination of the danger.

However, if the microcomputer malfunctions due to a failure of thecontrol section or the like, i.e., a so-called microcomputer runawayoccurs, in the dry cleaner disclosed in Japanese Unexamined PatentPublication No. 2005-218881, it will be impossible to control the steamvalve and hence to control the solvent gas concentration. In this case,the solvent gas concentration in the drum is increased, so that thedrying heater is liable to act as an ignition source to cause theignition of the solvent gas.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a main object of the present inventionto provide a highly safe dry cleaner which is free from the danger ofthe ignition and the like even if the microcomputer runaway occurs.

It is another object of the present invention to provide a dry cleanerwhich ensures safety in the drying process.

It is still another object of the present invention is to provide asafety circuit for a dry cleaner.

According to the present invention, there is provided a dry cleanerwhich performs a laundry washing process employing a flammable solvent,a liquid removing process and a drying process, and includes: atreatment tub in which laundry is contained, and the washing process,the liquid removing process and the drying process are performed; an aircirculation duct through which air taken out of the treatment tub flowsback to the treatment tub in a closed flow circuit in the dryingprocess; heating unit which heats the air flowing through the aircirculation duct; controller which controls operation of the heatingunit to perform the drying process; signal outputting unit which outputsa termination signal in response to completion of a predetermined liquidremoving operation performed in the treatment tub; and a safety circuitwhich maintains the heating unit in an inactive state irrespective of acontrol status of the controller unless the termination signal isoutputted.

The treatment tub may include a liquid-tight outer tub, an inner tubrotatably provided in the outer tub and configured to be rotated toremove the solvent from the laundry contained therein by a centrifugalforce, and a drive motor which rotates the inner tub. The signaloutputting unit may include a mechanism which outputs the terminationsignal after the inner tub or the drive motor is rotated at a rotationspeed not lower than a predetermined rotation speed level for apredetermined rotation period.

The signal outputting unit may include a switch which is turned on whenthe rotation speed of the inner tub or the drive motor is not less thanthe predetermined rotation speed level, and a timer which starts timemeasurement in response to the turn-on of the switch to measure a switchturn-on time during which the switch is turned on and, when the switchturn-on time reaches a predetermined period, outputs the terminationsignal.

The heating unit may include a heat exchanger which exchanges heat withthe air flowing through the air circulation duct, and steam supplyingunit which supplies steam to the heat exchanger. The safety circuit maybe configured to prevent the steam from being supplied from the steamsupplying unit to the heat exchanger to maintain the heating unit in theinactive state.

The steam supplying unit may include a steam supplying passage throughwhich the steam is supplied, and a valve which opens and closes thesteam supplying passage. The safety circuit may be configured toconstantly close the valve to maintain the heating unit in the inactivestate.

The steam supplying passage may include a plurality of steam supplyingpassages, and valves may be respectively disposed in the steam supplyingpassages. The safety circuit may be configured to constantly close apredetermined one of the valves to maintain the heating unit in theinactive state.

According to the present invention, the heating unit is maintained inthe inactive state by the safety circuit irrespective of the controlstatus of the controller unless the termination signal is outputted bythe signal outputting unit in response to the completion of thepredetermined liquid removing operation performed in the treatment tub.Further, the signal outputting unit is configured as a hardwarecomponent separate from the controller (a microcomputer and the like)and, therefore, provides the termination signal independently of thecontroller. Thus, actuation of the heating unit is permitted only afterthe completion of the predetermined liquid removing operation.

In general, the solvent gas concentration during the drying process isheavily dependent upon the amount of the solvent contained in thelaundry and the temperature of the air applied to the laundry.Therefore, the solvent gas concentration is liable to be increased, asthe contained solvent amount and the air temperature are increased. Byreducing the amount of the solvent contained in the laundry to apredetermined level or less in the liquid removing process, the amountof the solvent to be vaporized in the drying process is reduced and,even if the air temperature is high, there is no possibility that thesolvent gas concentration is increased to a predetermined concentrationlevel or higher.

Assuming, for example, that a flammable lower limit concentration (thelower limit concentration of the solvent gas at which the ignition ofthe solvent gas possibly occurs) is 0.8 vol %, an amount “A” of thesolvent contained in the laundry is herein defined such that, even iflaundry containing the solvent in an amount not greater than the solventamount “A” is overheated, the solvent gas concentration is maintained ata level not greater than 0.8 vol % (in the following description, “A” isthe solvent amount thus defined, unless otherwise specified). In thiscase, where the predetermined liquid removing operation according to thepresent invention is defined as a liquid removing operation to beperformed so as to reduce the amount of the solvent contained in thelaundry to a level not greater than “A”, the actuation of the heatingunit is permitted only after the amount of the solvent contained in thelaundry is reduced to the level not greater than “A”.

As a result, even if the controller runs away when the heating unit isin an active state, e.g., if the heating unit is brought into anuncontrollable state to overheat the air in the air circulation duct,there is no possibility that the solvent gas concentration exceeds theflammable lower limit concentration, because the amount of the solventcontained in the laundry is not greater than “A”. This ensures thesafety in the drying process. Thus, the dry cleaner is highly safewithout the danger of the ignition and the like.

According to the present invention, the signal outputting unit includesthe mechanism which outputs the termination signal after the inner tubor the driving motor is rotated at a rotation speed not lower than thepredetermined rotation speed level for the predetermined rotationperiod. Where the predetermined rotation speed level and thepredetermined rotation period are respectively defined as a rotationspeed and a rotation period which ensure that the amount of the solventcontained in the laundry after the liquid removing process can bereduced to a level not greater than “A”, the solvent gas concentrationis prevented from being increased to the predetermined concentrationlevel or higher by a simple method, i.e., by detecting the rotationspeed of the inner tub and the rotation period.

According to the present invention, the signal outputting unit includesthe switch which is turned on when the rotation speed of the inner tubor the drive motor is not lower than the predetermined rotation speedlevel, and the timer which starts the time measurement in response tothe turn-on of the switch to measure the switch turn-on time and, whenthe switch turn-on time reaches the predetermined period, outputs thetermination signal. Therefore, the solvent gas concentration isprevented from being increased to the predetermined concentration levelor higher by a simple method, i.e., by controlling the switch and thetimer.

According to the present invention, the heating unit includes the heatexchanger which exchanges heat with the air flowing through the aircirculation duct, and the steam supplying unit which supplies steam tothe heat exchanger. Further, the supply of the steam from the steamsupplying unit to the heat exchanger is prevented by the safety circuitto maintain the heating unit in the inactive state. Thus, the steam issupplied to the heat exchanger to heat the air flowing through the aircirculation duct only after the completion of the predetermined liquidremoving operation. As a result, even if the controller runs away duringthe supply of the steam, e.g., if a great amount of steam is suppliedfrom the steam supplying unit to steeply increase the temperature of theheat exchanger, the solvent gas concentration is prevented from beingincreased to the predetermined concentration level or higher, becausethe amount of the solvent contained in the laundry is not greater than“A”.

According to the present invention, the steam supplying unit includesthe steam supplying passage through which the steam is supplied, and thevalve which opens and closes the steam supplying passage. Further, thevalve is constantly closed by the safety circuit. With this arrangement,the solvent gas concentration is prevented from being increased to thepredetermined concentration level or higher by a simple controloperation, i.e., by constantly closing the valve.

According to the present invention, the steam supplying passage includesthe plurality of steam supplying passages, and the valves arerespectively disposed in the steam supplying passages. Further, thepredetermined one of the valves is constantly closed by the safetycircuit. For example, the predetermined one of the valves may be definedas a valve which possibly increases the solvent gas concentration to alevel higher than the flammable lower limit concentration when beingopened. In this case, the solvent gas concentration is prevented frombeing increased to the predetermined concentration level or higher byconstantly closing the thus defined valve. Further, there is no need tomaintain the other valves in an inactive state by the safety circuit.This obviates the need for providing an additional device, therebysaving costs.

The foregoing and other objects, features and effects of the presentinvention will become more apparent from the following detaileddescription of preferred embodiments with reference to the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of major portions of a dry cleaneraccording to one embodiment of the present invention.

FIG. 2 is a pipeline diagram of the dry cleaner shown in FIG. 1.

FIG. 3 is a block diagram illustrating the electrical construction ofthe dry cleaner shown in FIG. 1, particularly showing components relatedto the present invention.

FIG. 4 is a diagram illustrating a relay sequence controlling circuitwhich constitutes a solvent gas concentration safety system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS External Construction ofDry Cleaner

FIG. 1 is a front perspective view of major portions of a dry cleaner 1according to one embodiment of the present invention. Reference will bemade to directional arrows shown in FIG. 1 for directional notation.

Referring to FIG. 1, the dry cleaner 1 is, for example, for businessuse, and includes a generally rectangular box-shaped main body 2, and atank/filter kit 3 (see FIG. 2).

The main body 2 includes a rack-like frame 2 a. An outer tub 4 and adrum 5 (inner tub) accommodated in the outer tub 4 are provided withinthe frame 2 a. The frame 2 a is fixed to a floor. An operation panel 2 bis attached to a front face portion of the frame 2 a above the outer tub4, specifically, at around a level of user's eyes. A user operatesoperation buttons 66 (to be described later) of the operation panel 2 bto cause the dry cleaner 1 to perform desired operations by, and theoperation status of the dry cleaner 1 is displayed on a display panel 67(to be described later) of the operation panel 2 b.

The outer tub 4 is of a generally rectangular box shape, and has agenerally cylindrical space defined therein. The outer tub 4 has anouter tub opening 4 a formed in a front wall thereof as communicatingwith the inside thereof and having a round shape as seen from the frontside. An annular metal rim 4 b is fitted along the periphery of theouter tub opening 4 a. An annular packing 4 c is attached to an innerperipheral front edge of the rim 4 b. The rim 4 b has a hinge 4 dprovided at a left edge portion thereof, and an engagement projection 4e provided at a right edge portion thereof. A door (not shown) isattached to the hinge 4 d so as to be pivotal about a pivot shaft of thehinge 4 d to open and close the outer tub opening 4 a. The door (notshown) has an engagement projection (not shown) provided at a portionthereof opposite from the hinge side. When the door (not shown) closesthe outer tub opening 4 a, the engagement projection (not shown) of thedoor is engaged with the engagement projection 4 e of the rim 4 b,whereby the door (not shown) is locked with the outer tub opening 4 aclosed.

Four corners of a bottom face of the outer tub 4 are connected to theframe 2 a via dampers 2 c. Therefore, even if the outer tub 4 vibratesduring the operation of the dry cleaner 1, the vibrations of the outertub 4 are damped by the dampers 2 c and hence prevented from beingpropagated around the dry cleaner 1 through the frame 2 a.

The drum 5 has a generally cylindrical hollow shape, and is disposedwith its center shaft extending generally horizontally, specifically,extending anteroposteriorly. A drum motor 21 (see FIG. 3) connected tothe center shaft of the drum 5 is disposed behind the drum 5. A drivingforce generated by rotation of the drum motor 21 is transmitted to thedrum 5 through the center shaft to rotate the drum 5. The drum 5 has adrum opening 5 a formed in a front wall thereof at a positioncorresponding to the outer tub opening 4 a as communicating with theinside of the drum 5. The drum opening 5 a is anteroposteriorly opposedto the outer tub opening 4 a. Therefore, laundry can be loaded into thedrum 5 through the outer tub opening 4 a and the drum opening 5 a withthe door (not shown) being opened. A plurality of baffles 5 b areprovided on an inner peripheral surface of the drum 5 as projectingtoward the center shaft.

Internal Construction of Dry Cleaner

FIG. 2 is a pipeline diagram of the dry cleaner 1. With reference toFIG. 2, the internal construction of the dry cleaner 1 will hereinafterbe described in detail.

The outer tub 4 has an air inlet 6 through which air is introduced intothe drum 5, and an air outlet 7 through which the air is expelled fromthe drum 5. The air outlet 7 and the air inlet 6 are connected to eachother through a circulation duct 8 (air circulation duct). That is, thecirculation duct 8 is regarded as a closed circuit (closed flow circuit)which has the air inlet 6 and the air outlet 7 and connects the airoutlet 7 and the air inlet 6 to each other.

The dry cleaner 1 is an apparatus designed to perform a dry cleaningprocess with the use of a special flammable solvent (e.g., apetroleum-based solvent or the like). The dry cleaning process isadvantageous in that laundry is less liable to shrink and oil stains aremore easily removed as compared with a water cleaning process in whichthe laundry is washed with water. On the other hand, it is not desirableto release the solvent used for the dry cleaning to the externalenvironment. Therefore, the dry cleaner according to this embodiment isof a type which is adapted to recover all the used solvent.

More specifically, a predetermined amount of solvent supplied from atank 31 to be described later is contained in the outer tub 4, and thelaundry is washed with the solvent in a washing process. After thewashing process, the solvent is recovered from the outer tub 4 into thetank 31. Further, the drum 5 is rotated at a higher speed to removeresidual solvent from the laundry. The removed solvent is also recoveredinto the tank 31. Thereafter, a drying process is performed to dry thelaundry by circulating the air between the circulation duct 8 and thedrum 5 while rotating the drum 5 at a lower speed. The vapor of thesolvent resulting from vaporization of the solvent from the laundry inthe drying process is also recovered by condensation thereof. During therotation of the drum 5, the laundry is agitated by the baffles 5 b.Thus, the laundry is efficiently washed and dried.

In the drying process, a blower 10 is rotated by a blower motor 9,whereby the air in the drum 5 is circulated from the air outlet 7 intothe air inlet 6 through the circulation duct 8. Drying coolers 11 and 12are provided in the circulation duct 8, and a drying heater 13 (heatexchanger) is provided adjacent the air inlet 6. The air flowing out ofthe drum 5 into the circulation duct 8 through the air outlet 7 containsthe vaporized solvent (solvent gas). The air containing the solvent gasis cooled by the drying coolers 11 and 12, so that the solvent gas inthe air is liquefied. That is, the solvent-containing air flowingthrough the circulation duct 8 is cooled by the drying coolers 11 and12, whereby the solvent is condensed and recovered from the air.Thereafter, the air is heated by the drying heater 13, and the heatedair is supplied as drying air into the drum 5 through the air inlet 6.In the drum 5, the heated air is heat-exchanged with the laundry,whereby the solvent contained in the laundry is vaporized. The vaporizedsolvent flows together with the air into the circulation duct 8 throughthe air outlet 7. This cycle in which the air is circulated between thedrum 5 and the circulation duct 8 is repeated, thereby drying thelaundry in the drum 5. The dry cleaner 1 is configured such that thedrying air from the air inlet 6 is supplied to the laundry in the drum 5through the outer tub opening 4 a and the drum opening 5 a. The drumopening 5 a is an opening having the greatest size in the drum 5, sothat the drying air can be efficiently supplied to the laundry throughthe drum opening 5 a. Further, the air in the drum 5 is circulatedthrough the circulation duct 8. Therefore, the air heated by the dryingheater 13 and supplied into the drum 5 is heat-exchanged with thelaundry in the drum 5 to vaporize moisture (solvent) from the laundry,and then reused for the drying of the laundry rather than being expelledtogether with the vaporized moisture to the outside. Accordingly, thedry cleaner 1 is environmentally friendly.

Meanwhile, the solvent is flammable. Therefore, there is the danger ofignition or explosion of the vaporized solvent unless the temperature ofthe heated air is reliably controlled in the drying process.

For detecting the temperature of the heated air supplied into the drum 5from the air inlet 6, a drum inlet temperature thermistor 14 and aninlet over-temperature preventing thermistor 15 are provided downstreamof the drying heater 13 (on a downstream side with respect to an airflow direction—this definition holds true for the following description)in the circulation duct 8. Though not shown, the inlet over-temperaturepreventing thermistor 15 is connected to a transistor circuit, andconfigured such that the circuit is cut off through the transistor, forexample, when a temperature of 95° C. is detected. Therefore, the inletover-temperature preventing thermistor 15 is advantageous in that itensures more accurate detection of an operation temperature and aquicker response to the temperature than a thermostat.

For detecting the temperature of the air expelled from the air outlet 7,a drum outlet temperature thermistor 16 and an abnormal outlettemperature judging thermistor 17 which monitors the drum outlettemperature thermistor 16 to check whether or not the drum outlettemperature thermistor 16 malfunctions are provided in the circulationduct 8. For detecting the temperature of the air cooled by a downstreamone of the two drying coolers 11 and 12, a cooler temperature thermistor18 and a cooler over-temperature preventing thermistor 19 whichconstitutes a part of a safety circuit are provided in the circulationduct 8.

Further, an aspiration port 20 and a gate valve V14 are provided betweenthe drying cooler 12 and the drying heater 13 in the circulation duct 8for regulating the internal pressure of the circulation duct 8 when thecirculation duct internal pressure is excessively increased. Normally,the aspiration port 20 is opened, and the gate valve V14 is opened topermit the air to flow through the circulation duct 8. Further, thecirculation duct 8 has an explosion protection port 26 which, if thesolvent gas-containing air flowing through the circulation duct 8happens to be ignited to cause explosion, releases the blast of theexplosion. The explosion protection port 26 is biased in a closingdirection by a spring not shown.

The drying coolers 11 and 12 are connected to a freezing machine 23through coolant passages 22 a, 22 b and 22 c. The freezing machine 23 isdisposed outside the main body 2. When a drying cooler electromagneticvalve 2Y inserted in the coolant passage 22 a is opened, a coolant(e.g., cooling water) flows from the freezing machine 23 into the dryingcooler 12 and the drying cooler 11 through the coolant passages 22 a and22 b, whereby the drying cooler 12 and the drying cooler 11 perform acooling operation. The drying coolers 11 and 12 are herein connected inseries with each other to the freezing machine 23, but may be connectedin parallel with each other to the freezing machine 23. Morespecifically, the coolant passages 22 a and 22 c may be provided foreach of the drying coolers 11 and 12 to supply the coolant individuallyto the drying coolers 11 and 12 from the freezing machine 23. Of course,freezing machines 23 may be respectively provided for the drying coolers11 and 12.

The drying heater 13 is a so-called radiator which radiates heat ofsteam passing therethrough from fins thereof to heat the ambientatmosphere, and is connected to a steam passage 24 (steam supplypassage) and a steam passage 25. More specifically, the steam passage 24connects an external steam source to the drying heater 13. An inletvalve V20 is inserted in the steam passage 24. The steam passage 24 isbranched into a first steam supply passage 24 a having a relativelygreat passage diameter and a second steam supply passage 24 b having arelatively small passage diameter between the drying heater 13 and theinlet valve V20. A first valve V27 is inserted in the first steam supplypassage 24 a, and a second valve V28 is inserted in the second steamsupply passage 24 b. In this embodiment, a path extending from the steampassage 24 to the drying heater 13 corresponds to the heating unitaccording to the present invention. On the other hand, the steam passage25 is a passage through which the steam supplied from the steam passage24 to the drying heater 13 is expelled to the outside.

With the inlet valve V20 and the first valve V27 and/or the second valveV28 being opened, steam (e.g., steam at 110 to 120° C.) is supplied tothe drying heater 13, whereby the drying heater 13 heats the air in thecirculation duct 8 by the steam. Since the first steam supply passage 24a and the second steam supply passage 24 b are different in steam supplycapacity, the steam may be supplied to the drying heater 13 from one orboth of the first steam supply passage 24 a and the second steam supplypassage 24 b as required.

In the drying process, the rotation of the blower motor 9, and theopening and closing of the inlet valve V20 and the first valve V27and/or the second valve V28 are typically controlled based ontemperatures detected by the drum inlet temperature thermistor 14, thedrum outlet temperature thermistor 16 and the cooler temperaturethermistor 18. In the dry cleaner 1, a safety circuit 70 (to bedescribed later) is constituted by an electric circuit which controlsthe opening and closing of the first valve V27 and the second valve V28for prevention of the ignition and explosion of the solvent gas. Theelectric circuit for controlling the opening and closing of the valvesV27, V28 will be described in detail later.

The tank/filter kit 3 includes the tank 31 which stores the solvent, anda first filter 32 and a second filter 33 which are connected in seriesfor filtering the solvent pumped up from the tank 31. A pump-up pipe 34is connected to a bottom of the tank 31 at one end thereof. A valve V1is inserted in the pump-up pipe 34. The other end of the pump-up pipe 34is connected to a junction 35. A solvent pump 36 is connected to thejunction 35 on its suction side and to an inlet of a three-way valve V6on its ejection side. One outlet of the three-way valve V6 is connectedto one end of a flow pipe 37, and the other end of the flow pipe 37 isconnected to the tank 31 via a valve V19. The flow pipe 37 is branchedat its intermediate portion (between the three-way valve V6 and thevalve V19) to be connected to the serial connection of the first filter32 and the second filter 33. A flow pipe 38 is connected to an outlet ofthe second filter 33, and a distal end of the flow pipe 38 is connectedto an inlet of a solvent heat exchanger 39 provided in the main body 2.

A bypass pipe 40 is connected to the other outlet of the three-way valveV6 at one end thereof, and the other end of the bypass pipe 40 joins theflow pipe 38 connected to the inlet of the solvent heat exchanger 39.

Therefore, the solvent is applied to the solvent heat exchanger 39through the first filter 32 and the second filter 33, or applied to thesolvent heat exchanger 39 through the bypass pipe 40 with the filters 32and 33 bypassed by switching between the outlets of the three-way valveV6.

A steam pipe 41 and a coolant pipe 42 are provided in the solvent heatexchanger 39. The steam pipe 41 and the coolant pipe 42 are each wound,for example, in a coil shape. Steam passages 43 and 44 are connected tothe steam pipe 41. The steam passage 43 connects the steam pipe 41 andthe steam passage 24, and a valve V21 is inserted in the steam passage43. On the other hand, the steam passage 44 is a passage through whichthe steam supplied from the steam passage 43 to the steam pipe 41 isdischarged to the outside. With the valve V21 being opened, the steamflows into the steam pipe 41 through the steam passage 43 to bedischarged through the steam passage 44. While the solvent passesthrough the solvent heat exchanger 39, the steam pipe 41 at a hightemperature exchanges heat with the solvent to heat the solvent. On theother hand, coolant passages 45 a and 45 b are connected to the coolantpipe 42, and a solvent cooler electromagnetic valve 3Y is inserted inthe coolant passage 45 a. With the solvent cooler electromagnetic valve3Y being opened, the coolant passes through the coolant pipe 42. Whilethe solvent passes through the solvent heat exchanger 39, the coolantpipe 42 exchanges heat with the solvent to cool the solvent. Bycontrolling the opening and closing of the valve V21 and the opening andclosing of the solvent cooler electromagnetic valve 3Y, the solvent heatexchanger 39 is switched to heat or cool the solvent, whereby thetemperature of the solvent passing through the solvent heat exchanger 39is regulated at a desired temperature level.

A flow pipe 46 is connected to an outlet of the solvent heat exchanger39 at one end thereof. The other end of the flow pipe 46 is connected toan inlet of a three-way valve V9. A liquid temperature thermistor 47 formeasuring the temperature of the solvent and a liquid over-temperaturepreventing thermistor 48 for preventing a liquid temperature from beingincreased to a predetermined temperature level or higher are provided inthe flow pipe 46.

A soap concentration sensor 50 is provided downstream of these twothermistors in the flow pipe 46.

A liquid supply pipe 51 is connected to one outlet of the three-wayvalve V9 at one end thereof and to the outer tub 4 at the other endthereof, so that the solvent can be supplied into the drum 5. A feedbackpipe 52 is connected to the other outlet of the three-way valve V9 atone end thereof and to the tank 31 at the other end thereof.

A recovery pipe 62 for recovering the solvent condensed by the dryingcoolers 11 and 12 in the circulation duct 8 has one end connected to apotion of the circulation duct 8 below the drying coolers 11 and 12. Theother end of the recovery pipe 62 is connected to a water separator 63.In the water separator 63, water contained in the recovered solvent isseparated, and the separated water is drained through a drain pipe 64.Then, the recovered solvent is returned into the tank 31 through arecovery pipe 65.

The outer tub 4 has a drain port 55 provided at its lowermost portion,and a liquid surface detection chamber 56 is connected to the drain port55. The liquid surface detection chamber 56 is provided with two liquidsurface switches, i.e., a standard liquid surface switch 57 and a drainliquid surface switch 58. The liquid surface detection chamber 56 alsoserves as a trap which traps a button or the like dislodged from thelaundry and falling through the drain port 55 during the washingprocess.

A recovery pipe 59 is connected to a lower end of the liquid surfacedetection chamber 56 at one end thereof. A valve V4 is inserted in therecovery pipe 59. The other end of the recovery pipe 59 is connected tothe junction 35.

A soap pipe 61 is connected to a soap container 60 at one end thereofand to the junction 35 at the other end thereof. A valve V17 is insertedin the soap pipe 61.

Next, the flow of the solvent will be described with reference to thepipeline diagram of FIG. 2.

In the washing process, the solvent stored in the tank 31 is suppliedinto the drum 5 (the outer tub 4). At this time, the solvent pump 36 isdriven with the valve V1 being opened, with the three-way valve V6 beingopened to the flow pipe 37 and with the valve V19 being closed. Thus,the solvent in the tank 31 flows into the flow pipe 38 through the firstfilter 32 and the second filter 33 and, after the temperature of thesolvent is regulated by the solvent heat exchanger 39, the solvent flowsto the three-way valve V9 through the flow pipe 46. With the three-wayvalve V9 being opened to the liquid supply pipe 51, the solvent issupplied into the outer tub 4 through the liquid supply pipe 51. Duringthe supply of the solvent, the valve V4 is closed. The amount of thesolvent contained in the outer tub 4 is detected by the standard liquidsurface switch 57 and, when a predetermined amount of the solvent(suitable for the washing) is contained in the outer tub 4, the valve V9is switched so as to close the liquid supply pipe 51 and open thefeedback pipe 52.

A soap is preliminarily mixed with the solvent contained in the tank 31and, when the solvent passes through the flow pipe 46, the concentrationof the soap in the solvent is measured by the soap concentration sensor50. If the soap concentration is lower, the soap is pumped up from thesoap container 60 through the soap pipe 61 with the valve V17 beingopened, and mixed with the supplied solvent.

During the supply of the solvent to the outer tub 4, the three-way valveV6 may be switched, as required, to cause the solvent to bypass thefilters 32, 33, so that the solvent is applied to the solvent heatexchanger 39 through the bypass pipe 40 and then supplied to the outertub 4.

In a solvent draining and removing process, the solvent pump 36 isdriven with the valve V4 being opened and with the valve V1 beingclosed. The solvent is returned into the tank 31 with the three-wayvalve V6 being opened to the flow pipe 37 and with the valve V19 beingopened.

Alternatively, the solvent flowing through the flow pipe 37 may becaused to flow through the filters 32 and 33, the flow pipe 38, thesolvent heat exchanger 39 and the flow pipe 46 with the valve V19 beingclosed, and then flow through the three-way valve V9 and the feedbackpipe 52 back into the tank 31. Thus, the solvent drained from the outertub 4 after the washing process and the solvent removed from the laundryby the centrifugal force are passed through the filters 32 and 33 fordecontamination, and then returned into the tank 31.

Electrical Construction of Dry Cleaner 1

FIG. 3 is a block diagram illustrating the electrical construction ofthe dry cleaner 1, particularly showing components related to thepresent invention.

The dry cleaner 1 includes a control section 81 (controller) whichincludes, for example, a microcomputer and the like.

The operation buttons 66 and the display panel 67 provided on theoperation panel 2 b are connected to the control section 81. When theuser operates the operation buttons 66, an input signal corresponding tothe button operation is inputted to the control section 81. An outputsignal indicating the operation status of the dry cleaner 1 is inputtedto the display panel 67, whereby the operation status is displayed inthe form of alphanumeric information on the display panel 67.

The three-way valve V9, the valve V4 and the drum motor 21 (drive motor)to be controlled are connected to the control section 81, and theiroperations are controlled by the control section 81. In the washingprocess, for example, the three-way valve V9 is opened to the liquidsupply pipe 51 to supply the solvent into the drum 5 (the outer tub 4).In the liquid removing process, the valve V4 is opened to return thesolvent removed from the outer tub 4 into the tank 31.

The first valve V27 and the second valve V28 are connected to thecontrol section 81 via the safety circuit 70.

The safety circuit 70 is electrically connected to the drum motor 21, aspeed detector 68 and a timer 69. The rotation speed of the drum motor21 is detected by the speed detector 68. The timer 69 is actuateddepending on the detection of the rotation speed, and a signal of thetimer 69 is inputted to the safety circuit 70. The control section 81 ispermitted to control the operation of the first valve V27 only after thesafety circuit 70 is turned on in response to the signal inputted fromthe timer 69. On the other hand, the control section 81 is permitted tocontrol the operation of the second valve V28 even if the safety circuit70 is in an OFF state. A specific configuration of the safety circuit 70will be described in detail with reference to FIG. 4.

Solvent Gas Concentration Safety System

FIG. 4 is a diagram illustrating a relay sequence controlling circuit 71which constitutes a solvent gas concentration safety system. The solventgas concentration safety system is herein defined as a system whichprevents the ignition and explosion of the solvent gas in the dryingprocess. For this system, the dry cleaner 1 includes the relay sequencecontrolling circuit 71.

The relay sequence controlling circuit 71 is a control circuit whichcontrols the first valve V27 and the second valve V28, and includes, forexample, a parallel connection circuit which is connected to a DC powersource (e.g., DC24V) and connects the first valve V27 and the secondvalve V28 as control objects in parallel. Further, the relay sequencecontrolling circuit 71 includes a first switch 77 and a second switch 78which are connected in series with the first valve V27 and the secondvalve V28, respectively, and controlled by the microcomputer in thecontrol section 81. When the first switch 77 and the second switch 78are controlled to be turned on, ON signals are respectively inputted tothe first valve V27 and the second valve V28, whereby the valves V27 andV28 are opened.

A second contact 76 a of a second relay 76 is further connected inseries with the serial connection of the first valve V27 and the firstswitch 77. Thus, the safety circuit 70 is configured such that the firstvalve V27 is maintained in an inactive state irrespective of the ONcontrol of the first switch 77 performed by the control section 81unless the second contact 76 a is in an ON state.

The relay sequence controlling circuit 71 further includes a detectioncircuit 79 for controlling the second contact 76 a.

The detection circuit 79 is connected in parallel with the safetycircuit 70, and has a serial connection of the second relay 76 and afirst contact 75 a of a first relay 75, and a serial connection of thefirst relay 75 and a timer contact 69 a of the timer 69 which isconnected in parallel with the aforesaid serial connection.

The first relay 75 and the second relay 76 are devices such aselectromagnetic relays each functioning to open and close a contact byan electromagnetic force. When electric current flows through anelectromagnetic coil (not shown) provided in the relay 75 or 76, thecontact 75 a or 76 a is closed.

A door switch 74 for detecting the state of the door (not shown) whichopens and closes the outer tub opening 4 a is connected in series withthe parallel connection of the first relay 75 and the second relay 76.The door switch 74 is turned on when the door is closed.

The timer 69 is connected in parallel with the door switch 74 and thefirst relay 75 (the door switch 74 and the second relay 76), andconfigured such that the timer contact 69 a of the timer 69 is turned onafter a lapse of a predetermined period from the start of timemeasurement in response to the signal input. The timer 69 is connectedin series with a detection switch 73 and, when the detection switch 73is turned on, a time measurement starting signal is inputted to thetimer 69.

The detection switch 73 is incorporated in an internal circuit (notshown) of the speed detector 68 connected to the drum motor 21 (see FIG.3). The drum motor 21 has, for example, an inverter circuit incorporatedtherein to be frequency-controlled, and the speed detector 68 isconnected to the inverter circuit. The speed detector 68 is configuredso as to detect a frequency outputted when the drum motor 21 is rotatedat a rotation speed not lower than a predetermined rotation speed leveland to maintain the detection switch 73 in an ON state during therotation of the drum motor 21 at the rotation speed not lower than thepredetermined rotation speed level.

Next, the control sequence of the relay sequence controlling circuit 70will be described.

When the liquid removing process is started after the completion of thewashing process, the drum 5 is rotated at a high speed by a rotativedriving force of the drum motor 21 to remove the solvent from thelaundry. When the rotation speed of the drum motor 21 is increased to500 rpm or higher, for example, a frequency output corresponding to therotation speed not lower than 500 rpm is detected by the speed detector68, and the detection switch 73 is turned on.

Upon the turn-on of the detection switch 73, an ON signal is inputted tothe timer 69 from the detection switch 73, and the timer 69 starts timemeasurement. If the ON state of the detection switch 73, i.e., therotation of the drum motor 21 at 500 rpm or higher, thereafter continuesfor 4 minutes, for example, the timer contact 69 a is turned on. In thewashing process and the liquid removing process, the door (not shown)for opening and closing the outer tub opening 4 a is closed, so that thedoor switch 74 is maintained in an ON state.

With the timer contact 69 a being in an ON state, electric current flowsthrough the electromagnetic coil provided in the first relay 75 to turnon the first contact 75 a. With the first contact 75 a being in an ONstate, electric current flows through the electromagnetic coil providedin the second relay 76 to turn on the second contact 76 a. Thus, thecontrol section 81 is permitted to control the turn-on of the firstswitch 77, whereby electrical conduction between the positive side andthe negative side of the first valve V27 is established to open thefirst valve V27.

If the speed detector 68 detects a drum motor rotation speed of 500 rpmor higher but the rotation of the drum 5 at this rotation speed does notcontinue for 4 minutes as measured by the timer 69, the second contact76 a is in an OFF state. Therefore, even if the control section 81 turnson the first switch 77, the ON signal of the first switch 77 is nottransmitted to the first valve V27, so that the first valve V27 ismaintained in the inactive state. That is, the control section 81 ispermitted to turn on the first valve V27 only after the drum 5 isrotated at a rotation speed of 500 rpm or higher for 4 minutes for theremoval of the solvent from the laundry.

As a result, even if the steam is continuously supplied to the dryingheater 13, for example, due to runaway of the microcomputer of thecontrol section 81 to apply high temperature air to the laundry in thedrying process, the solvent gas concentration does not exceed theflammable lower limit concentration (e.g., 0.8 vol %). This is becausethe solvent has been removed by a certain amount from the laundry in theliquid removing process. Thus, the safety is ensured in the dryingprocess, so that the dry cleaner 1 is highly safe without the danger ofthe ignition and the like. Further, the safety control is easilyachieved simply by operating the detection switch 73 and the timer 69.

Further, the second valve V28 has a smaller steam supply capacity thanthe first valve V27. Even if the steam is continuously supplied to thedrying heater 13 through the second valve V28, the temperature of thedrying heater 13 is not significantly increased. This eliminates theneed for controlling the second valve V28 by the safety circuit 70without the danger that the solvent gas concentration exceeds theflammable lower limit concentration. As a result, there is no need toincorporate an additional relay and the like in the circuit, therebysaving costs.

It should be understood that the present invention be not limited to theembodiment described above, but various modifications may be made withinthe purview of the claims.

In the embodiment described above, for example, the first valve V27 ispermitted to be opened on the condition that the drum is rotated at arotation speed of 500 rpm or higher for 4 minutes for the removal of thesolvent from the laundry. However, this condition is an exemplarycondition. The condition for opening the first valve V27 is not limitedto the aforementioned one, but may be such that the liquid removingprocess is performed for a longer period as long as the resultingsolvent gas concentration does not exceed the flammable lower limitconcentration.

In the embodiment described above, the opening/closing control isperformed on the first valve V27 by way of example. Alternatively, theopening/closing control may be performed on the inlet valve V20 providedin the steam passage 24 serving as a steam supply source for supplyingthe steam to the first valve V27.

While the embodiment of the present invention has been described indetail, it should be understood that the embodiment is merelyillustrative of the technical principles of the present invention butnot limitative of the invention. The spirit and scope of the presentinvention are to be limited only by the appended claims.

This application corresponds to Japanese Patent Application No.2006-313317 filed in the Japanese Patent Office on Nov. 20, 2006, thedisclosure of which is incorporated herein by reference.

1. A dry cleaner which performs a laundry washing process employing aflammable solvent, a liquid removing process and a drying process, thedry cleaner comprising: a treatment tub in which laundry is contained,and the washing process, the liquid removing process and the dryingprocess are performed; an air circulation duct through which air takenout of the treatment tub flows back to the treatment tub in a closedflow circuit in the drying process; heating unit which heats the airflowing through the air circulation duct; controller which controlsoperation of the heating unit to perform the drying process; signaloutputting unit which outputs a termination signal in response tocompletion of a predetermined liquid removing operation performed in thetreatment tub; and a safety circuit which maintains the heating unit inan inactive state irrespective of a control status of the controllerunless the termination signal is outputted.
 2. The dry cleaner accordingto claim 1, wherein the treatment tub includes: a liquid-tight outertub; an inner tub rotatably provided in the outer tub and configured tobe rotated to remove the solvent from the laundry contained therein by acentrifugal force; and a drive motor which rotates the inner tub,wherein the signal outputting unit includes a mechanism which outputsthe termination signal after one of the inner tub and the drive motor isrotated at a rotation speed not lower than a predetermined rotationspeed level for a predetermined rotation period.
 3. The dry cleaneraccording to claim 2, wherein the signal outputting unit includes: aswitch which is turned on when the rotation speed of one of the innertub and the drive motor is not less than the predetermined rotationspeed level; and a timer which starts time measurement in response tothe turn-on of the switch to measure a switch turn-on time during whichthe switch is turned on and, when the switch turn-on time reaches apredetermined period, outputs the termination signal.
 4. The dry cleaneraccording to any of claim 3, wherein the heating unit includes: a heatexchanger which exchanges heat with the air flowing through the aircirculation duct; and steam supplying unit which supplies steam to theheat exchanger, wherein the safety circuit is configured to prevent thesteam from being supplied from the steam supplying unit to the heatexchanger to maintain the heating unit in the inactive state.
 5. The drycleaner according to claim 4, wherein the steam supplying unit includes:a steam supplying passage through which the steam is supplied; and avalve which opens and closes the steam supplying passage, wherein thesafety circuit is configured to constantly close the valve to maintainthe heating unit in the inactive state.
 6. The dry cleaner according toclaim 5, wherein the steam supplying passage includes a plurality ofsteam supplying passages, and valves are respectively disposed in thesteam supplying passages, wherein the safety circuit is configured toconstantly close a predetermined one of the valves to maintain theheating unit in the inactive state.
 7. The dry cleaner according toclaim 1, wherein the heating unit includes: a heat exchanger whichexchanges heat with the air flowing through the air circulation duct;and steam supplying unit which supplies steam to the heat exchanger,wherein the safety circuit is configured to prevent the steam from beingsupplied from the steam supplying unit to the heat exchanger to maintainthe heating unit in the inactive state.
 8. The dry cleaner according toclaim 7, wherein the steam supplying unit includes: a steam supplyingpassage through which the steam is supplied; and a valve which opens andcloses the steam supplying passage, wherein the safety circuit isconfigured to constantly close the valve to maintain the heating unit inthe inactive state.
 9. The dry cleaner according to claim 8, wherein thesteam supplying passage includes a plurality of steam supplyingpassages, and valves are respectively disposed in the steam supplyingpassages, wherein the safety circuit is configured to constantly close apredetermined one of the valves to maintain the heating unit in theinactive state.
 10. A safety circuit for a dry cleaner, comprising: aswitch which is turned on when a rotation speed of one of an inner tubfor being rotated to remove solvent from a laundry contained therein bya centrifugal force and a drive motor for rotating the inner tub is notless than a predetermined rotation speed level; and a timer which startstime measurement in response to the turn-on of the switch to measure aswitch turn-on time during which the switch is turned on and, when theswitch turn-on time reaches a predetermined period, outputs atermination signal.